What Are Mutations?
• Changes in the nucleotide sequence of
DNA
• May occur in somatic cells (aren’t passed to offspring)
• May occur in gametes
(eggs & sperm) and be passed to offspring

Are Mutations Helpful or
Harmful?
• Mutations happen regularly
• Almost all mutations are neutral
• Chemicals & UV radiation cause mutations
• Many mutations are repaired by enzymes

Are Mutations Helpful or
Harmful?
• Some type of skin cancers and leukemia result from somatic mutations
• Some mutations may improve an organism’s survival (beneficial)

Chromosome Mutations
• May Involve:
– Changing the structure of a chromosome
– The loss or gain of part of a chromosome

Chromosome Mutations
• Five types exist:
– Deletion
– Inversion
– Translocation
– Nondisjunction
– Duplication

Deletion
• Due to breakage
• A piece of a chromosome is lost

Inversion
• Chromosome segment breaks off
• Segment flips around backwards
• Segment reattaches

Duplication
• Occurs when a gene sequence is repeated

Translocation
• Involves two chromosomes that aren’t homologous
• Part of one chromosome is transferred to another chromosomes

Translocation

Nondisjunction
• Failure of chromosomes to separate during meiosis
• Causes gamete to have too many or too few chromosomes

Chromosome Mutation
Animation

Gene Mutations
• Change in the nucleotide sequence of a gene
• May only involve a single nucleotide
• May be due to copying errors , chemicals , viruses , etc.

Types of Gene Mutations
• Include:
– Point Mutations
– Substitutions
– Insertions
– Deletions
– Frameshift

Point Mutation
• Change of a single nucleotide
• Includes the deletion, insertion, or substitution of ONE nucleotide in a gene

Point Mutation
• Sickle Cell disease is the result of one nucleotide substitution
• Occurs in the hemoglobin gene

Frameshift Mutation
• Inserting or deleting one or more nucleotides
• Changes the “ reading frame ” like changing a sentence
• Proteins built incorrectly

Frameshift Mutation
• Original:
– The fat cat ate the wee rat .
• Frame Shift (“a” added):
– The fat c a a tet hew eer at.

Amino Acid Sequence
Changed

Gene Mutation
Animation